I picked up a used Lensless Camera Co 5x7. The seller thought it was the 5" model but after I got it I measured 4" from front to film holder location. I asked Lensless Camera about mine but they couldn't recall making any 4" models. Wondering if anyone who owns a 5" model could check the focal length measurement. I don't have any problems with trying my 4" model but just curious if anyone else might have one.